Oral Pathology Lectue Note- Odontogenic Tumours(Part 1)

• Odontogenic tumors comprise a complex group of lesions with varied histopathological and clinical features.
• Some tumors are true neoplasms, while some are hamartomas (developmental malformations).
• Some are composed only of odontogenic epithelium, while many are mixed i.e. both epithelium and mesenchyme, while some are composed only of mesenchyme

TUMORS OF ODONTOGENIC EPITHELIUM: -

1. Ameloblastoma

2. Calcifying epithelial odontogenic tumor

3. Adenomatoid odontogenic tumor

4. Squamous odontogenic tumor

            5. Clear cell odontogenic tumor

TUMORS OF ODONTOGENIC EPITHELIUM & MESENCHYME WITH / WITHOUT DENTAL HARD TISSUE FORMATION: -

           1. Ameloblastic fibroma & Ameloblastic fibrosarcoma.

           2. Ameloblastic fibro odontoma

           3. Odontoameloblastoma

           4. Odontoma – Compound & Complex

TUMORS OF ODONTOGENIC MESENCHYME WITH / WITHOUT DENTAL HARD TISSUE FORMATION: -

          1. Odontogenic fibroma

          2. Odontogenic myxoma

          3. Cementoblastoma

          4. Granular cell odontogenic tumor

AMELOBLASTOMA

Most common odontogenic neoplasm, derived from odontogenic epithelium.

Slowly growing, locally aggressive, benign neoplasm.

Occurs in 3 different types with differing clinical, radiological and histological features.

                1. CONVENTIONAL / MULTICYSTIC

                2. UNICYSTIC

                3. PERIPHERAL

AMELOBLASTOMA - CONVENTIONAL

CLINICAL FEATURES: -

• Age incidence: 3^rd & 4^th decades.
• Sex incidence: Slightly more in males.
• Site predilection: 80% ameloblastomas occur in posterior  mandible, followed by maxillary molar         region.

Signs & symptoms: -

   

• Slowly growing, painless, hard bony swelling or expansion of jaw.
• Thinning of cortical plates produces “Egg shell crackling”.
• Other symptoms – Tooth mobility  root resorption and paresthesia if inferior alveolar nerve is affected. 

RADIOLOGICAL FEATURES: -

• Typically rounded, well defined multilocular radiolucency with scalloped margins.
• When loculations are large, the appearance is called as “SOAP BUBBLE” appearance.
• When loculations are smaller, the appearance is called “HONEY COMBED” appearance.
• Buccal & lingual cortical plates are expanded.
• Roots of adjacent teeth displaced / resorbed.
• As it spreads through medullary spaces, radiographic margins are not accurate indication of bone involvement.

DIFFERENTIAL DIAGNOSIS: -

  ODONTOGENIC KERATOCYST

  FIBROUS DYSPLASIA

  OSSIFYING FIBROMA

  CENTRAL GIANT CELL GRANULOMA

HISTOPATHOLOGICAL FEATURES: -

Many subtypes are seen.

1.       FOLLICULAR

2.       PLEXIFORM

3.       ACANTHOMATOUS

4.       GRANULAR CELL

5.       DESMOPLASTIC

6.       BASAL CELL TYPE

7.       CLEAR CELL Type

AMELOBLASTOMA (FOLLICULAR)

• Islands of epithelium resemble dental organ surrounded by mature connective stroma.
• Individual follicles show central mass of stellate reticulum like cells surrounded by a single peripheral layer of ameloblast like cells.
• Nuclei of peripheral cells are reversely polarized.
• Within the islands, cyst formation is common.

                                               

AMELOBLASTOMA (PLEXIFORM)

• Instead of islands, long, anastomosing cords and occasional sheets of epithelial cells bounded by columnar / cuboidal cells.
• Cells within cords are more loosely arranged than peripheral cells.
• Supporting stroma is loose and vascular.
• Cyst formation occurs, not inside follicles, but in surrounding stroma.

                                               

AMELOBLASTOMA (ACANTHOMATOUS)

• Central area of follicles show extensive squamous metaplasia, often associated with keratin formation.
• DOEAS NOT INDICATE A MORE AGGRESSIVE COURSE OF TUMOR.
• Can be confused with squamous cell carcinoma.

AMELOBLASTOMA (GRANULAR CELL)

• Follicles / sheets of cells show granular cell change.
• These cells have abundant cytoplasm filled with eosinophilic granules.
• Seen in younger persons and appears to be more aggressive clinically.

AMELOBLASTOMA (DESMOPLASTIC)

• This variant is composed of small islands / cords of odontogenic epithelial cells surrounded by a dense, collagenized stroma.
• Peripheral ameloblast like cells are missing / inconspicuous around the islands / cords.
• Occurs in anterior jaw and radiologically looks like a fibro-osseous lesion due to mixed opacity & lucency.

                                               

AMELOBLASTOMA (BASAL CELL)

• Least common type.
• Composed of nests / sheets of hyperchromatic basaloid cells.
• No stellate reticulum present centrally and peripheral cells tend to be cuboidal rather than tall columnar.

TREATMENT: -

• Can vary from simple enucleation to curettage to en bloc resection.
• As lesion spreads through medullary spaces, simple enucleation can leave islands of tumor within the jaws, leading to recurrence.
• Marginal resection is the optimal method.
• Rarely can undergo malignant transformation.

                                                                                                               

UNICYSTIC AMELOBLASTOMA

Controversy, whether it arises de novo or as neoplastic transformation of odontogenic cyst lining.

CLINICAL FEATURES: -

• Age incidence: Young individuals.
• Sex incidence: males.
• Site predilection: 90% cases occur in post  mandible.
• Signs & Symptoms: Asymptomatic swelling of jaws. Many lesions contain a tooth inside.

                                                                                               

RADIOLOGICAL FEATURES: -

• Typically seen as well defined, unilocular ‘lucency, many times surrounding the neck of impacted 38 or 48 – impossible to distinguish from dentigerous cyst.
• Occasionally, may be seen unassociated with teeth – then they nay be diagnosed as OKC or a radicular cyst.

DIFFERENTIAL DIAGNOSIS: -

        Odontogenic cysts like – Dentigerous, OKC, radicular etc.

        Odontogenic tumors like – Ameloblastoma, AOT, CEOT etc.

                                                                                                               

HISTOPATHOLOGICAL FEATURES: -

Three variants are recognized.

                1. LUMINAL UNICYSTIC

                2. INTRALUMINAL UNICYSTIC

                3. MURAL UNICYSTIC

                                                                                                               

UNICYSTIC - LUMINAL

• Tumor is confined to luminal surface of cyst.
• Seen as fibrous cyst wall with lining comprised totally / partially of ameloblastic epithelium, showing a basal layer of columnar / cuboidal reversely polarized cells.
• Overlying epithelial cells are loosely adhesive, resembling the stellate reticulum of dental organ.

                                               

UNICYSTIC - INTRALUMINAL

• This variant shows the tumor from cyst lining protruding into the lumen of cyst.
• Intraluminal projections resemble plexiform ameloblastoma in most cases, though not always.                                       

UNICYSTIC - MURAL

In this type, the fibrous wall of the cyst is infiltrated with typical follicular / plexiform ameloblastoma.

Believed to be more aggressive than other two variants.

                               

AMELOBLASTOMA (PERIPHERAL)

• Typically presents as non ulcerated, sessile / pedunculated gingival mass.
• Must be differentiated from other more common gingival swellings.